1. Field of the Invention
The present invention relates to an improvement of an implanting article such as artifical bones, teeth root, etc.
2. Description of the Prior Art
As conventional implanting material using apatite, such prior arts is disclosed in Japanese published patent applications No. 50349/1980, "Dental compound material" and No. 45814/1981, "Hydroxy Apatite ceramic material and the manufacturing method thereof". Such state respectively that apatite has a favorable affinity with live bones, and also, a molded article made of a mixture of apatite and resin material can be used for an implanting article.
Apatite is a ceramic material mainly composed of calcium phosphate and, its mechanical strength and impact resistance are both poor. According to clinical experiences, apatite can be used only for covering broken parts of bone undergoing comparatively lower stress, but it is difficult for apatite to be applied to bone-joint portions or dental use.
Also, as described in the aforesaid "Dental compound material" (Japanese published patent application No. 50349/1980), articles prepared by homogeneously dispersing apatite particles in the mother material made from synthetic resin, etc. has been known.
The dental compound material may be molded into column shape artificial bones shown respectively in FIGS. 1(a), (b) and (c). The artificial bones are used as implanting articles for a thighbone. One of the dental compound materials is a mixture of polyethylene resin and apatite particles of 100 .mu.m-500 .mu.m in diameter. Another is an implanting material for dental use and is composed of a mixture of phenol resin and apatite particles.
However, these dental compound materials are a mixture of a mother material and apatite particles with a volmetric rate of from 9:1 to 4:6. The materials are molded into an artificial bone by heating while stirring, and finished to desired shapes. In this case, a required large density of apatite appeared on the surface of the resulting article is satisfied, but a great deal of apatite particles are also homogeneously dispersed to the center thereof (hereinafter this method is referred to as whole dispersion-manufacturing method).
Thus prepared artifical bones have poor strength, especially an inadequate impact resistance, so when these are used for long duration as an implanting article, deformation of breaking down may well occur. Accordingly, it was found that the processing for whole homogeneous dispersion of apatite over the mother material is not necesarily proper according to the kind of usage.
Moreover apatite dispersed into the center part of the artficial bones has no effect on affinity will organic bones, and also acts to lower the strength of the articles.